1. Field of the Invention
This invention relates to apparatus and methods for obtaining three-dimensional images from two-dimensional images on either film or videotape.
2. Prior Art
In the 1920s an optical illusion was discovered which has been referred to as the Pulfrich effect or illusion. In order to be elicited, it requires constant motion under very defined conditions. It is able to utilize a single image rather than the conventional dual image. Its discovery resulted in the fact that if one eye is shaded somewhat darker than the other, the exact amounts of which have been discussed in detail in two patents, U.S. Pat. Nos. 4,131,342 and 4,705,371, three dimensional (3-D) viewing is possible. In these two patents, respective inventors Leslie P. Dudley and Terry D. Beard discuss various aspects concerning the illusion of depth that is conferred on the individual viewing the phenomenon. The present investigators have confirmed that only one eye needs shading, and have discovered that the shading, as manifested in a lens, need only be gray and/gradations there of.
Outdoor scenes facilitate the 3-D effect because there is considerable background. Nevertheless, in order to achieve good 3-D, it is also necessary to have very close (to the camera) foreground. This combination with the subject inbetween makes ideal 3-D, whether a dual image or the Pulfrich illusion is to be used.
During the nearly 70 years that have passed since the Pulfrich illusion was discovered, little commercial use has been made of it, other than Dudley's attempt at animation, until Beard and others tried to capture the illusion live, specifically, during the 1989 Pasadena Rose Parade and then the Super Bowl halftime show of the same year.
The Pulfrich illusion requires constant motion in order for the in-depth perception to be achieved. Unfortunately, when viewed with angular camera motion that is not constant in angular velocity or radius, or with both eyes shaded with different neutral-density value filters, many people develop various types of eye strain. These may include double vision or blurred vision, resulting in vertigo or headaches. The present invention enables people engaged in the shooting of stereoscopic illusions using the Pulfrich effect to overcome the problems inherent in capturing the illusion and, at the same time, to reduce the problems associated with viewing it. The shortcoming of the previous applications when used for this purpose will be addressed, and the means of overcoming such shortcomings disclosed.